Governor mechanism



July 30, 1935. A. SCHWENDNER ,90

GOVERNOR MECHANISM Filed June 7, 1934 6 Sheets-Sheet l WITNESSES:

INVENTOR F. SCHWINDNER.

mam

ATTORNEY July 30, 1935. s w fl 2,009,417

GOVERNOR MECHANISM Filed June 7, 1934 6 Sheets-Sheet 2 INVENTOR v nmnmvF.5cnwzuousn.

BY QJIV5'VQ ATTORNEY July 30, 1935.

A. F. SCHWENDN ER GOVERNOR MECHANISM 6 Sheets-Sheet 3 INVENTOR FiledJune 7, 1934 WITNESSES:

ANTHONY F. Scnwsuom-zn.

M -QM ATTORNEY y 1935. A. F. SCHWENDNER I 2,009,417

GOVERNOR MECHANISM Filed June 7, 1954 6 Sheets-Sheet 4 WITNESSES:INVENTOR f w /L F16 4 ANTHONY F SCHWENDNER ATTORNEY y 1935- A. F.SCHWENDNER 2,009,417

GOVERNOR MECHANISM Filed June 7, 1934 6 Sheets-Sheet 5 FIa.5.

HIGH PRESSURE OIL FROM GOV- IMPELLER TRRNSF'ORMIO OIL TO VR LVEMECHRNISH INVENTOR ANTHONY F. SCHWENDNEH ATTORNEY Patented July 30, 1935PATENT OFFICE GOVERNOR MECHANISM Anthony F. Schwendner, Essington, Pa.,assignor to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application June 7, 1934,Serial No. 729,370

16 Claims.

My invention relates to control apparatus for prime movers, for example,steam turbines, and it has for an object to provide a governing systemwhich is stable and capable of operating with a small percentage ofregulation.

A further object of my invention is to provide a governor of thepressure transformer type which utilizes a small range of primary fluidpressure change, the primary fluid pressure being developed as afunction of the speed of the prime mover, to secure a large range ofsecondary or transformed fluid pressure used to actuate the governor oradmission valve means.

A further object of my'invention is to provide a prime mover governor ofthe fluid pressure type wherein fluid pressure developed as a functionof the speed of the prime mover is applied to a sealed expansiblechamber of transformer governing apparatus, whereby minimum flow offluid under primary pressure is required.

A further object of my invention is to provide a pressure transformerwherein frictional resistance is minimized.

A further object of my invention is to provide 25 a turbine installationhaving a governor valve, a throttle valve and an emergency governor,with a transformer governor constructed and arranged so that, in case ofoverspeeding of the turbine to a predetermined extent, not only is thethrottle valve closed, but the transformed or secondary pressureutilized to actuate the governor valve is released, whereby closure ofthe governing valve is assured.

A further object of my invention is to provide a turbine-installation,having a governor valve, a throttle valve, and an emergency governorwith a transformer governor subject, respectively, both to a backpressure regulator and to primary pressure of fluid developed as afunction of the speed of the turbine, the transformer governorbeingconstructed and arranged so that, in case of over'speeding of theturbine, not only is the throttle valve closed, but also the transformedor secondary pressure is released to permit closure of the governorvalve.

These and other objects are effected by my invention, as will beapparent from the following description and claims, taken in connectionwith the accompanying drawings, forming a part of this application, inwhich:

Fig. 1 is a diagrammatic view of an embodiment of my improved controlsystem; I

Fig. 2 is a view similar to Fig. 1 but showing a .15 modified form .ofthe control system;

Fig. 3 is a sectional view of the transformer governor shown in Fig. 1;

,Fig. 4 is a sectional view of a transformer governor employed with theembodiment shown in Fig. 2;

Fig. 5 is a sectional view showing a modified form of pressuretransformer;

Fig. 6 is a sectional view of of Fig. 2;

Fig. 7 is a diagrammatic view showing a fur- 10 ther embodiment of myinvention: and

Fig. 8 shows an alternative form of accumulator means.

Referring now to the drawings more in detail,

I show a prime mover, for example, a steam tur- 5 bine, at In, includinga stator II and a spindle 12. One or more admission valve devices areshown at l3, each device including an admission valve l4 and aservo-motor 15 for opening and closing the valve.

The turbine is provided with primary pressureproducing means, at It, fordeveloping fluid under primary pressure and varying as a function of theturbine speed, the fluid under primary pressure being supplied to atransformer governor, at I1, which, in turn, supplies fluid undertransformed or secondary pressure to the servomotors l5 of the admissionor governor valves.

The transformer governor, at H, is constructed and arranged to utilize anarrow range of pri- 3o mary pressure change to secure a veryv much Iwider range of secondary pressure change so that very small changes inprimary pressure are effective to secure response of the steam valve.

The primary fluid pressure producing means, at I6, is constructed andarranged to provide such pressure with very little fluid flow so thatpower consumption for this purpose is Accordingly, I prefer to use theprimary pressure producing means disclosed and claimed in theapplication of O. N. Bryant, Serial No. 728,257, filed May 31, 1934, andassigned to the Westinghouse Electric & Manufacturing Company and whichpressure producing means will now be briefly described. The spindle I2is provided with an impeller I! of the centrifugal type supplying fluidunder pressure to the annular chamber l9 provided in the statorstructure, the annular chamber supplying fluid through an orifice 20 tothe primary pressure passage 2| communicating with a centrifugal escapedevice comprised preferably by the annular chamber 22 and the diagonalpassage 23 formed in the spindle.

One end of the passage 23 communicates continuously with the annularchannel 22' and the the servo-motors other end communuicates with adrain. It will, therefore, be apparent that the pressure existing in thepassage 2| and the annular chamber 22 will depend upon the spindlespeed, for, the more rapid the rotation of the spindle, the greater willbe the centrifugal effect of the oil column in the diagonal passagebetween the spindle axis and the channel 22; and, in consequence, thepressure in the passage 2| will be modulated to vary substantially asthe square of the turbine speed.

The orifice 20 serves as means for supplying fluid under pressure to thepassage 2|, but it restricts the rate of flow so that pressure in thepassage 2| may be varied as a function of the turbine speed in themanner just referred to. The other end of the passage 2| communicateswith the transformer governor, at H.

The transformer governor, at H, includes a housing 25 having an upperchamber 26, an intermediate chamber 21, and a cylinder 28. A sylphon orbellows 29 has its upper end connected to the wall of the chamber 26 andits lower end connected to an abutment 30. A smaller bellows or sylphon3| is connected, at its upper end, to the abutment 30 and, at its lowerend, to the bottom wall of the chamber. Hence, the large and smallsylphons 29 and 3|, together with the housing 25, provide a sealedprimary pressure chamber 32 with which the primary pressure line 2|communicates, whereby negligible flow of fluid under primary pressure isrequired so that, not only are impulses quickly transmitted, but thepower requirements of the primary pressure producing means areminimized.

As the sylphon 3| is of smaller diameter than the upper sylphon 29, itwill be apparent that a lower annular primary piston area 33 is providedby the lower face of the abutment element 30, the primary pressuresupplied by the line 2 I being effective against the annular piston area33 to secure upward movement of the abutment 30 and the lower end of thesylphon 29. This upward movement is resisted by a spring 34 whosecompression is varied by a movable spring abutment 35; and means, suchas a screw member 36, is provided for moving the abutment upwardly anddownwardly, the screw being turned in any suitable manner by a speedchanger motor 31.

A spinner piston valve 38 fits the valve cylinder 28 and it has upperand. lower piston valve portions 40 and 4| separated by the annularspace 42. (See Figs. 3 and 4.) The lower piston portion 4| normally justlaps a pressure supply port 43 connected to the pressure supply passage44; the intermediate annular space 42 continuously communicates with thesecondary pressure supply passage 45; and the upper piston portion 40laps the exhaust 46. i

It will, therefore, be apparent that, with downward movement of thepiston valve, the-high pressure port 43 will be placed in communication,due to the annular space 42, with the secondary pressure supply passage45 to increase the secondary or transformed pressure; and, with upwardmovement of the piston valve 38, the secondary or transformed pressurepassage 45 will be placed in communication with the exhaust 48 connectedto the drain system 41.

The spinner piston valve 38 extends vertically across the intermediatechamber 21 through the wall structure separating the intermediate andupper chambers, and within the small sylphon 3| to contact with theabutment 30, the upper end of the piston valve having a thrust bearing48 preferably having single point contact with respect to abutmentstructure 30. The spinner piston 38 is preferably maintained in contactwith the abutment structure 30 due to the fact that secondary pressureis applied to the secondary or lower piston area 49 at the lower end ofthe piston valve 38.

The thrust bearing between the abutment 30 and the spinner piston valve38 has minimum pressure exerted thereon, with the result that a veryefficient thrust bearing, preferably of the point type may be used. Thereason for this is that the abutment structure 30 has the opposedprimary fluid pressure and springforces applied thereto without suchforces being imposed on the thrust bearing, the thrust bearing merelyhaving to carry sufficient load to move the piston valve when theabutment structure moves in a direction toward the spinner piston valve,fluid pressure being utilized to cause the spinner piston valve tofollow the motion of the abutment when the latter moves in the oppositedirection. Hence, as the thrust bearing is subject to minimum load,minimum resistance to rotation of the spinner valve occurs.

Thus, it will be seen that the piston valve 38 tends to assume anequilibrium position in which the forces of the primary and secondarypressures applied to the primary and secondary piston areas 33 and 49,respectively, are counterbalanced by the force of the spring 34. Ifthere is a change in primary pressure, then the equilibrium of forces isdisturbed, and, consequently, the piston valve 38 moves to securemodification of the secondary or transformed pressure, the latteroperation continuing until the change in secondary pressure issuflicient to compensate for the change in primary pressure when thepiston valve will be restored to neutral or cut-off position.

From the transformer governor structure so far described, it will beapparent that an increase in primary pressure tends to move the abutment30 upwardly, the spinner piston valve 38 following the abutment, butupward movement of the piston valve bringsabout reduction in secondarypressure, and, consequently, reduction in the pressure applied to thesecondary piston face 49, this reduction in secondary pressurecontinuing until the force of the secondary pressure acting on thesecondary face 49 is sufficiently reduced so that the spring 34.actingagainst the force of the primary pressure applied to the primary pistonarea 33 may move the piston valve 38 downwardly to its normal or neutralposition.

If there is a reduction in primary pressure, the spring causes theabutment 30 to move downwardly, the piston valve 38 being pusheddownwardly, and the secondary pressure supply passage being placed incommunication with the high pressure port 43, whereupon there willfollow an increase in secondary pressure, the secondary pressureincreasing until the force thereof acting on the secondary pressure face49 is sufficient to compensate for the reduction in primary pressureforce acting on the primary piston face 33 in order that the spring andthe fluid pressure forces may again be in equilibrium, at which time thepiston valve 38 will be in neutral cut-off position.

The secondary pressure supply passage 45 is connected to the admissionvalve servo-motors I5.

To overcome static friction and to make the transformer governor moreeffective, the pilot valve is provided with turbine means to securecontinuous spinning thereof. To this end, the

to move downwardly more than it would if the pilot valve has a rotor 50against which is impinged motive fluid by the jet 50', the jet 50' beingsupplied from any suitable source, for example, from the high pressurepassage 44.

An important feature of the present invention is to provide agovernor'which is highly responsive to load change. To this end, thesecondary pressure applied to the secondary piston area 49 of thetransformer is modified. The secondary or transformed fluid underpressure is supplied through an orifice 5| to the space or expansiblechamber 52 below the secondary piston face or area 49, and an airchamber or bell 53 is in communicatlon with the space 52. Preferably,the orifice area is adjusted by means of the needle valve 54.

For a given load, it will be apparent that there will be primary andsecondary pressures which are related as determined by the primary andsecondary piston areas, the secondary pressure also existing in thespace below the secondary piston area or face and in the air chamber. Ifthere is a gradual change in load, the piston valve 38 follows themotion of the abutment structure so that the secondary pressure changesin accordance with the change in primary pressure without lag; however,with rapid change in load, and consequently with rapid change in primarypressure, flow through the needle valve orifice is not sufficientlyrapid to cause the pressure applied to the secondary piston face tochange as rapidly as does the primary pressure, with the result that thepressure acting on the secondary piston face or area is effective, withthe primary pressure, to produce over-travel of the piston valve andthereby to produce a greater extent of secondary pressure change thanwould be called for by the change in primary pressure. For example,assume a rapid drop in load, the turbine speed and the' primary pressurerapidly increase and the sylphon moves upwardly in consequence thereof.The piston valve follows the motion of the sylphon causing reduction insecondary pressure; however, due to the needle valve orifice, thepressure below the secondary piston face or area 49 cannot decline sorapidly, with the result that increased effort is applied to the pistonvalve to move the latter upwardly to reduce the secondary pressurequickly, the reduction in secondary pressure being carried to a greaterextent than would be called for by the primary pressure change. Thegovernor valve may, therefore, be closed before the closing speed isreached.

In other words, in this way, the governor is made responsive to the rateof change of speed so as to have an anticipating effect. With drop inload, as the device responds to the rate of change of speed, thegovernor valve may be operated upon before a change of substantialmagnitude is attained. With drop in load, at a sufliciently rapid rate,the steam supply may be entirely out off, thereby preventing furtheracceleration of the rotor and allowing for the valve to be reset to aposition to permit enough steam to be supplied to maintain the speed ofthe turbine for the load carried.

If there is a sudden increase in load, then the consequent suddendecrease in primary pressure causes the spring 34 to move the pistonvalve 38 downwardly, causing the secondary pressure to increase morerapidly than the pressure supplied to the secondary piston area or face49, and, consequently, the piston valve tends secondary pressure builtup rapidly below the secondary piston face or area. In other words,there would be a tendency for downward overtravel, and this wouldquickly bring about a change in secondary pressure to a greater extentthan called for by the primary pressure change. The governor valve may,for example, move to wide open position so as to suddenly provide anincreased supply of motive steam to the turbine, the governor valve thenbeing reset by the transformer as the primary and secondary pressuresare brought into normal relation with the secondary pressure applied tothe secondary piston area 48 and the primary pressure attaining a valuecorresponding to the speed for the load carried.

As soon as permitted by flow through the needle valve orifice,pressurebelow the secondary piston face or area 49 comes intoequilibrium with the secondary pressure, and this causes such motion ofthe piston valve that the secondary'pressure is changed to adjust thegovernor valve to a position corresponding to its normal speed at theexisting load point. In other words, the needle valve orifice and theair chamber cause operation in response to rate of change of speed sothat the required operation, depending upon the direction of change,occurs before substantial change in magnitude. the device may respondwithin a speed difference of a turn or a fractionof a turn of thespindle. On the other hand, if the device depended upon the extent ormagnitude of change, the element of anticipation and consequent quickresponse would be absentthere would be overspeeding with drop in loadand too great a speed drop with sudden increase in load. The action inresponse to rate of speed change causes the governor valve to closebefore the turbine reaches closing speed and to open wide before thespeed drops to a point corresponding to wide open position of the valve.

In addition to the orifice and the air chamber' or accumulator servingas an anticipator, these features introduce a time element in the operation of the mechanism preventing hunting and violent fluctuations in thesecondary or transformed pressure line. The adjustable orifice 5|restricts the rate of flow of secondary pressure to or from theexpansible chamber 52 formed in.

part by the secondary piston face 49. The orifice 5| and the air chamber53 work together to provide a desired time interval during whichpressure change occurs in the secondary expansible chamber 52. When theapparatus is installed, the orifice needle valve 54 is adjusted for bestoperation and then it is locked in place.

The high pressure passage 44 is supplied from a high pressure line orsystem 55 supplied by the pump 56. Fluid under high pressure ispreferably furnished from the line 55 for actuation of the servo-motoror motors l5.

In addition to the motive steam having to pass For example,

through the admission valve or'valves M, such 5 "by the branch 68 of theorifice line 63. I will be seen that, upon release of the orifice line63 connected to the high pressure line 55 through an orifice 64.

The passage 63 has a branch 65 going to the trip valve 66 of theautostop or emergency governing mechanism, at 61, and a branch 68 goingto the trip valve, at 69, the apparatus operating so that, when theemergency governor is effective, the pressure in the line 63 is suddenlyreduced, the orifice 64 preventing rapid replenishment thereof, so thatthe spring of the throttle valve is effective to secure sudden closurethereof and the trip valve, at 69, is operated as hereinafter pointedout.

The autostop oremergency governor is of the usual type, the turbinespindle I2 being provided with a diametrically extending pin 18 in thediametrically-extending chamber II and the pin is held normally ininactive position by a spring 12. The center of gravity of the pin I8 isarranged sufliciently eccentric and the spring 12 of such force ischosen that, when a predetermined overspeed of the turbine is attained,the pin 18 suddenly flies radially outward, thereby acting on thetripping mechanism, at I3, to release pressure applied to the spring I4to hold the valve 66 closed, whereupon the latter valve opens, therebypermitting of release of pressure in the orifice line 63 and thebranches 65 and 68 for the purposes just stated.

Referring to the trip valve, at 69, this comprises an upper cylinder I6and a somewhat shorter lower cylinder 11 of larger diameter than thecylinder 16. A piston valve I8 is arranged in the cylinders. Thesecondary or transformed pressure supply line 45 is provided with arelease passage I9, which communicates with the upper portion of thecylinder 16. A drain passage 88 communicates with the cylinder 16 asuitable distance below the point of communication of the releasepassage I9 so that the piston portion 8| of the piston valve I8 isnormally effective to interrupt communication between the passages I9and 88; however, as hereinafter pointed out, with downward movement ofthe piston valve I8, the secondary release passage 19 is placed incommunication with the drain, whereupon the secondary or transformedpressure in the line 45 is released in order to bring about closure ofthe servo-motor or motors of the admission valves.

Both the high pressure line- 55 and the high pressure passage 44communicate with the cylinder I6, the point of communication beingpreferably at the same level and piston portions 82 and 88, with theannular space 84 therebetween preferably normally affordingcommunication between the high pressure passage 55 and the supplypassage 44, but, with downward movement of the piston valve 18, thepiston portion 82 interrupts such communication, thereby cutting off thesupply of high pressure fluid to the transformer governor. I

The piston valve 18 has connected to the lower end thereof a piston 86arranged in the lower cylinder 11, a spring 81 preferably actingdownwardly on the piston and the piston being forced upwardly by theforce of fluid pressure supplied Thus, it

pressure, not only will the throttle valve close, but also the pilotvalve 18 of the trip device, at 69, will move downwardly to release thesecondary or transformed pressure and to interrupt the supply of highpressure fluid to the transformer governor.

The servo-motors, at l5, may be of any suitable type so long as they areeffective to bring about closure of the governor or admission valvesupon drop in secondary or transformed pressure. To this end, in Fig. 1,I show the servo-motor l5 comprised by a housing having an operatingcylinder 88 with an operating piston 89 therein, a spring 98 beingdisposed above the piston to exert its force thereon. The piston 89 ismoved by fluid pressure applied to its lower face in the manner to bepointed out, increase in fluid pressure causing upward movement of theoperating piston 89 until the fluid pressure force is in equilibriumwith the force of the spring 98 and reduction in fluid pressure forceapplied below the piston89 causing downward movement of the piston underinfluence of the'spring force.

Referring now to the means for applying and modifying fluid pressureapplied to the operating piston 89, it will be seen that the secondarypressure supply line 45 communicates with the annular space 9| formed atthe lower portion of the servo-motor housing or cylinder, the governorvalve stem 92 extending through the annular portion. The valve stem orrod 92 has radial passages 93 communicating with an axial passage 94 toafford communication between the annular space 9| and the interiorcylinder 95 of the operating piston structure.

A passage 96 communicates with the space below the operating piston 89and the interior of the cylinder 95 and a passage 91 communicates withthe cylinder 95 at a point below the point of communication therewith ofthe passag e 96 and it communicates with the annular space 98 formedabout the operating piston.

.A pilot valve 99 is arranged in the cylinder 95, a scale spring I88being disposed in the cylinder and tending normally to move the pilotvalve 99 downwardly. The pilot valve 99 is moved upwardly against theforce of the spring I88 by secondary pressure applied through thepassage 94 and acting against the lower piston portion I8I carried bythe pilot valve. The passage 96 is normally lapped by an intermediatepiston portion I82 of the pilot valve. With upward movement of the pilotvalve in response to an increase in secondary pressure, ensuing as aresult of decrease in primary pressure with increase in turbine load andspeed thereof, the pilot valve moves upwardly to establish communicationbetween the high pressure space 98 en compassing the operating pistonand the passage 96 communicating with the space below the operatingpiston, whereby the operating piston is raised by the high pressuresupplied from the high pressure line 56 until such time as the pistonportion I82 interrupts communication between the passages 91 and 96. Onthe other hand, with a decrease in secondary pressure, the pilot valvemoves downwardly to place the passage 96 in communication, through theport I 88, with the space above the piston valve, the latter space beingconnected with the drain 41; and, thereupon, the operating piston movesdownwardly until communication with the space below the operatingpiston, through the passage 96, is

I again interrupted. With release of the secondary or cut-off positionof the latter, it will be apparent that the spring force and, therefore,the secondary pressure, vary from a minimum to a maximum for completemovement in one direction of the operating piston and the connectedvalve and from maximum to minimum for complete movement in the otherdirection. Accord ingly, the spring I serves the required function of ascale spring customarily employed in a governing system.

The apparatus shown in Fig. 2 is generally similar to that alreadydescribed, except that the transformer governor, at I1, in addition tohaving primary pressure imposed thereon by the primary pressure line 2I,also has tertiary pressure applied thereto and derived from a backpressure regulator, at I06. Furthermore, different types of operatingdevices or servo-motors for the admission valves are shown at Ia. Inaddition, the secondary pressure release operative in response toautostop or emergency governor is modified.

Referring first to the back pressure regulator at I06, this may be ofany suitable type provided that requisite sensitivity is aiforded. Iprefer to use a regulator of the type shown and described in myapplication, Serial No. 729,372, filed June 7, 1934. Referring to Fig.2, it will be noted that the regulator includes a housing I01 providedwith upper and lower chambers I08 and I09 separated by body structureIIO providing a cylinder III. A piston valve H2 is disposed in thecylinder and it is arranged to place the outlet passage II3 either incommunication with the inlet passage II4 supplied from the impellerchamber I9 or with the exhaust passage I I5 communicating with the lowerchamber I09, the latter chamber being connected to the drain II6. Hence,with upward movement of the piston valve II2, pressure in the outlet II3will increase because of communication thereof with the pressure supplypassage II4. On the other hand, with downward movement of' the pistonvalve II2, pressure in the supply line I I3 will decrease because ofcommunication thereof with the exhaust. The pressure line II3communicates with the upperchamber 26 of the transformer governor so asto act on the upper face of the abutment 30 in the same direction as thespring 34.

From the structure described, it will be apparentthat the transformergovernor, at I1, of Fig. 2 operates exactly in the same manner as thetransformer governor in Fig. 1, except that an additional fluid pressureis applied thereto, fluid pressure from the back pressure regulator, atI05, being supplied by the passage II3 to the space above the abutment30. Therefore, not only does the transformer governor serve to controlthe admission of steam to the turbine in accordance with the load butalso controls the admission so as to maintain a predetermined backpressure. It will be obvious that the back pressure regulator may beused in any suitable manner; it may be associated with the line betweenhigh and low pressure turbines, with an inter-.

stage bleeder line, or with the back pressure line of a single turbine.

A back pressure steam connection H1 is connected, for example, to theconnection II8 between high and low pressure turbine elements, theconnection supplying steam to the chamber II9 so that its pressure maybe exerted on the' sylphon I20 arranged in the chamber, the sylphonhaving a piston or abutment face I2I which bears against a stem I 22carried by the abutment member I24, the latter bearing against the upperend of. the spring I25 as well as against the pointed end I26 of thepiston valve II 2.

The lower end of the piston valve I I2 has a point bearing connectionI21 with respect to an abutment I28 against which bears a spring I29arranged in the lower chamber I09. The lower end of the spring I29 isengaged by an adjustable abutment I30, the adjustment mechanismbeingpreferably constructed and arranged so as to prevent leakage on accountof adjustment. For the latter purpose, the abutment I30 is preferablymade cup-shaped as to enclose a bellows or sylphon I3I connected at itsupper end to the abutment or follower I33 and at its lower end to thelowermost wall of the lower chamber I09. The sylphon, therefore,provides space to accommodate the adjustment screw or member I32, whichmay have a connection with respect to the lower wall which is sealedfrom the interior of the lower chamber I09.

From the back pressure regulator structure so far described, it will beapparent that the piston valve H2 is subject to opposing forces, theforce of the spring I29 acting upwardly on the piston valve I I2 and theforce of the steam pressure acting downwardly, through the sylphonabutment, on the pilot valve against the force of the spring The pilotvalve has an upwardly facing piston face or area I33 to which fluidunder outlet pressure is supplied through the passage I34 containing anorifice provided by the needle valve I30, the purpose thereof being tosubject the pilot valve to the effect of the outlet pressure. Anaccumulator, for example, an air bell I31 communicates with the passageI34 at the piston area side of the orifice. Outlet pressure acting onthe piston area I33 tends to move thepiston valve II2 downwardly. v

Assuming an increase in back pressure, then the sylphon abutment I2Icauses downward movement of the piston valve II2 placing the impellerpassage H3 in communication with the exhaust II5, whereupon the pressureapplied tov the governing transformer abutment 30 will be decreased andthe transformer governor will operate to restrict the supply of steam tothe turbine. With a reduction in the outlet pressure brought about inthis way, the pressure applied to the piston face I 33 is also reduced,whereby the total of forces tending to cause the piston valve to movedownwardly is reduced, this reduction in outlet pressure continuinguntil the force thereof acting on the piston face I33 is sufficient tocounterbalance the back pressure force applied. due to increase in fluidpressure, whereby the piston valve is brought back to a neutral cut-01fposition. On the other hand, with a decrease in pressure, the contraryoperation takes place, the piston valve moving upwardly because of. thereduced steam pressure acting on the sylphon abutment I2l, therebyplacing the impeller passage II4 in communication with the outletpassage II3 to increase the pressure thereof; and the pressure in thepassage II3 will increase until such time as the increasing pressureapplied to the piston face I33 is sufllcient to compensate for thediminishing steam pressure, whereupon the piston valve will be broughtback to neutral or cut-ofi' position.

The piston valve preferably has spinning motion imparted thereto by anysuitable means, for

example, a turbine including a rotor I39 carried by the valve.

In Fig. 2, the autostop plunger 10 operates trigger mechanism 13 topermit a valve 66 to open in order to release the pressure in theorifice line 63. the latter having branches going to the throttle valve51 and to the valve trip device, at I40, the latter preferablyconsisting of a valve I which normally closes a port I42 of thesecondary pressure supply passage 45, the valve I having a piston I43pressed downwardly by a spring I44 and having the orifice line 63supplying pressuretherebelow. With opening of the autostop or emergencygovernor valve 61, the pressure in the orifice line 63 is suddenlyreleased, and the valve I4I moves downwardly under influence of thespring I44 to open the port I42 to drop the secondary or transformedpressure in the line 45.

In Figs. 2 and 6, there are shown servo-motor devices of a differenttype from that already described. Each serve-motor includes an operatingpiston I46 connected to a stem I46a, the stem being connected to thegovernor or admission valve. Each piston I46 is arranged in an operating cylinder I41 and the latter has spring means I48 therein and actingon top of the piston I46 so as to exert a biasing eifect thereon tendingto move the admission valve in a closing direction.

The piston I46 is moved upwardly and downwardly by means of fluid underpressure supplied to and exhausted through the passages I49 and I50 andcontrolled by a piston valve II.

The piston valve I 5| is arranged in a valve cylinder I52 having upperand lower high pressure ports I53 and I54, respectively, adjacent to theports I55 and I56 communicating with the passages I 50 and I49,respectively. Fluid under high pressure is supplied from the highpressure line 55 to the high pressure ports I53 and I 54.

The piston valve I5I is provided with suitablepiston portions I51, I58,I59 and I60 suitably spaced so as to afford communication with theports, the piston portions I58 and I59 normally lapping the ports I55and I56. If the piston valve moves upwardly, the upper passage I50 willbe placedin communication with the exhaust port I6I and the lowerpassage I49 will be placed in communication with the high pressuresupply port I54, whereupon the operating. piston I46 is caused to moveupwardly. On the other hand, if the pilot valve I5I is moved downwardly,pressure will be exhausted from below the piston I46 and applied to thespace thereabove.

Secondary pressure from the secondary pressure line 45 is supplied to achamber I 62 containing at its upper end a sylphon or bellows I63 havingan abutment I64. A tension spring I65 is connected to the abtument I64at one end and the other end of the spring is connected to a threadedscrew I66, whereby the spring pull acting in opposition to the secondarypressure may be suitably varied.

The upper end of the piston valve is connected to the lower end of thetension or scale spring I61, the scale of the latter being substantiallyless than that of the spring I65, the upper end of the spring I 61 beingconnected to one end of the follow-up lever I16, fulcrumed at anintermediate point I16a, the other end of the latter being pivotallyconnected to the valve rod I46a.

Assuming that there isv a decrease in load and consequent increase inspeed, the primary pressure delivered to the transformer increases andthe secondary pressure delivered by the latter through the conduit 45 tothe chamber I62 decreases. Therefore, due to this decrease in secondarypressure, the force thereof acting on the piston face I64 becomes lessand the consequent preponderating force of the load spring I65 causesthe pilot valve to be pulled down against the reduced secondary pressureand the tension of the scale spring I61 with the result that fluid underhigh pressure is supplied above the operating piston I46 and fluid belowthe latter is exhausted and the operating piston moves downwardly, suchdownward movement of the operating piston and movement of the admissionvalve ina closing direction continuing until such time as the increasedtension force of the scale spring is sufficient to overcome the loadspring to bring the pilot valve back to neutral or cut-off position.

On the other hand, should the turbine speed decrease due to increase inload, then the secondary pressure supplied to the chamber I62 wouldincrease thereby causing the pilot valve to move upwardly, with increasein the tension force of the load spring I65 and decrease in the tensionforce of the'scale spring I61; however, such movement of the pilot valvecauses motive fluid to be admitted below the operating piston and thelatter moves upwardly, and such upward movement of the operating pistonwill continue, the upward movement being accompanied by decrease in thetension force of the scale spring I61, until such time as the decreasein the tension force of the scale spring is sufiicient to counteract theincrease in tension force of the load spring I65, whereupon the pilotvalve will be restored to neutral or cutoif position. The scale springexerts maximiun tension force with the admission valve in closedposition and minimum tension force with the valve full open. In this waya scale effect is given to the governing system, there being a range ofsecondary pressures corresponding to the range of tension forces of thescale spring.

Thus, it will be seen that, under all conditions of operation, a changein secondary pressure is accompanied by movement of the pilot valve,such movement being resisted by the resultant of the tension forces ofthe load and scale springs and that the consequential movement of theoperating piston results in follow-up motion being applied to the scalespring so that the tension force thereof is modified in such manner thatthe load spring may restore the pilot valve to neutral or cut-offposition.

If desired, dash pot apparatus may be associated with the scale springto avoid hunting effects. To this end, I show the upper end of the scalespring connected to a screw member I69, the latter being held betweenthe head I of the stem I1I, pivotally connected to the upper end of thefollow-up lever I16, and a spring I12, the upper end of the spring I12bearing against the bottom of the inverted cup-piston I15. The stem I1Iextends through the bottom portion of the cup piston so that the'springI12 functions to hold the cup piston upwardly against suitable abutmentmeans at I1Ia. The cup piston i fits within the cylinder I68 so that thespace of the latter below the cup piston provides a displacementchamber. The cylindcr has an adjustable orifice at I68a, which restrictsto any desired extent the freedom of ingress and egress of fluid intoand out of the displacement chamber. The dash pot arrangement preventsjerky or hunting movements of the apparatus. It is to be understood, ofcourse, that the dash pot arrangement is an auxiliary device which mayor may not be used, as desired, for the scale spring is fully effectiveto accomplish its intended purposes, as just pointed out, without havingdash pot means associated therewith.

The dash pot comprised by the piston I14 and the cylinder I avoids jerkyor hunting movements of the apparatus.

In Fig. 5, I show a further form of transformer governor wherein theimpeller pressure is used as the source 01' supply for the transformedor secondary pressure. In this view, I show a housing structure I10having an upper chamber In, an intermediate chamber I80, and a cylinderhaving an upper portion I02 01' larger diameter than a lower portionI83.

A sylphon or bellows I is disposed in the upper chamber and has itsupper end connected to the wall thereof. The lower end of the sylphonhas an abutment I05 engaging the point bearing I" of the spinner pistonvalve structure I31. A compression spring I" bears at its bottom againstthe abutment I 05 and has its upper end engaged by a follower I" whichis adjusted upwardly and downwardly bythe speed changer motor I".

The piston valve structure III has an impeller or turbine element ISIarranged in the intermediate chamber I80, 9. piston portion I32 disposedin'the cylinder portion I02 of larger diameter and defining a downwardlyfacing secondary piston face I93 and a piston portion I34.

Oil under primary pressure is supplied from the impeller to the passageI36 for action against the primary pressure face afforded by thesylphon. Also, fluid is supplied from the passage I96 to the jet Ilia toimpart spinning motion to the rotor IOI to avoid static friction of thepiston valve structure.

With an increase in primary pressure, the

sylphon abutment I85 will be caused to move upwardly; and, as the pistonI has a groove Ifla affording communication between the high pressureport and the space below the piston,

primary pressure also acts upwardly on the lowerface I35 of the pistonportionJll, the spinner piston structure will thereby be caused tofollow the motion of the sylphon, but, immediately uponsuch-upwardmovement, a groove I31 cut in the piston element I32 afiordscommunication of the secondary pressure space or passage IS! with theexhaust or drain, whereupon the secondary pressure declines, whereby theupward acting secondary force acting on the piston face I33 is reducedsufliciently so that the spring may overcome the increased primary forceto move the piston valve Ill back to neutral or cut-off position. 0n theother hand, with a decrease in impeller pressure, the contrary operationtakes place, the piston valve structure I31 moving downwardly underinfluence of the spring I" due to decrease in impeller pressure, causingthe groove IS! in the lower piston valveportion I to place the highpressure supply passage 200 in communication with the secondary passageI90, so as to increase the secondary or transformed pressure, thisincrease continuing until the increasing secondary pressure force actingon the piston face I93 in an upward direction is 2 sufficient tocounteract the diminishing primary orifice 202 and an air bell 203 isarranged between the needle valve and the servo-motor. This arrangement,while giving governor control of the base load machine, avoids responseto frequency fluctuations. Where the tubine and its connected generatorare used for base load operation, it is desirable to avoid disturbanceof the governing system on account of frequency fluctuations, it beingcustomary to have the base load generator connected to a systemsupplied'by other generators. Frequency disturbances may, therefore, beimposed on the rotary parts of the base load machine and thesedisturbances would react on the governing system and the admission valvecontrolled thereby unless the arrangement shown in Fig. '7 wereemployed. While frequency fluctuations may produce fluctuations insecondary pressure supplied by the passage 45, the secondary pressurefluctuations are substantially damped or absorbed by the cooperation ofthe orifice 202 and the air chamber 203 arranged at the admission valveside of the orifice, whereby the governor is efiectiveto control theadmission valve to secure admission of steam suitable to loadrequirements 'without the latter being afiected by frequencyfluctuations.

With a transformer governor, such as shown in Fig. 1, and the needlevalve 20I and the air bell or chamber 203 arranged in the line betweenadjusting the needle valve 20I to restrict the bers being shown at 53,I31 and 203, it will be apparent that other types of accumulator meansmay be used. For example, in Fig. 8, I show the expansible chamber forthe piston area subject to secondary or outlet pressure formed in partby a bellows 205 whose expansion or distention is resisted by the spring206, the force of the latter being varied by the follower 201 carried bythe threaded stem 208. The bellows form is advantageous in that there isno chance of the accumulator becoming ineffective because of loss ofair.

From the foregoing, it will be apparent that as the governing mechanismis of the pressure transformer type, it is highly sensitivev to speedchanges. Sensitivity of the transformer governor is increased by havinga spinner piston valve and also by having such valve relieved of primarypressure and spring forces so that mini-mum pressure occurs in thethrust bearing between the spinner piston valve and the abutmentstructure the admission valve means adjusted to admit the proper amountof steam to operate the turbine at the speed required for the load, butit may anticipate rapid changes in load so as to minimize changes inspeed or be made to operate more sluggishly depending upon the need.Furthermore, the pressure transformer governor cooperates in peculiarways with other elements of the power plantinstallation: the governor isadapted to be acted upon by back pressure regulator, the operation beingso sensitive that the regulator performs its function of holding theback pressure within a very narrow range of variation; the governorapparatus is peculiarly suitable for primary pressure developing meansof low power consumption, this advantage following from thecharacteristic of the governor of being responsive to pressure changewithout requiring any flow on account of leakage; and the transformer,due to its particular arrangement of parts and connections, provides foran advantageously cooperative arrangement with pressure controlled partsof the plant such as the admission and throttle valves and the emergencygovernor, the pressure system or systems therefor being speciallyarranged to cooperate with features of the transformer governor.

-While I have shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications, without departing from thespirit thereof, and I desire, therefore, that only such limitationsshall be placed thereupon as are imposed by the prior art or as arespecifically set forth in the appended claims.

What I claim is:

1. In combination, means providing fluid under primary pressure; acylinder having an inlet port supplied with fluid under pressure, anexhaust connection, and a secondary pressure port; means providing asupply passage communicating with the secondary pressure port; a pistonvalve movable from an intermediate cut-ofl? position, in one direction,to establish communication of the secondary port with the inlet port,and, in the other direction, to establish communication of the secondaryport with the exhaust connection, whereby the secondary or transformedpressure in the supply passage is varied; a movable abutment providedwith a piston area; a thrust bearing between one end of the piston valveand the abutment; means providing for the application of fluid underprimary pressure to the abutment piston area; biasing means having itsforce acting on the abutment in opposition to the force of the primarypressure; means providing a secondary piston area on the piston valve;means for supplying fluid under secondary pressure to the secondarypiston area; said secondary piston area being so disposed that, withmovement of the piston valve in consequence of primary pressure change,the force of the resulting secondary pressure, is effective to restorethe I piston valve to neutral or cut-off position; and

means for imparting spinning motion to the piston valve.

. 2. In combination, means providing fluid under primary pressure; acylinder having an inlet port supplied with fluid under pressure, anexhaust connection, and a secondary pressure port; means providing asupply passage communicating with the secondary port; a piston valvemovable from an intermediate cut-off position, in one direction, toestablish communication of the secondary port with the inlet port, and,in theother direction, to establish communication of the secondary portwith the exhaust connection, whereby secondary or transformed pressureof fluid in the supply passage may be varied; an abutment; a thrustbearing between one end of the piston valve and the abutment; saidabutment having a piston area at the thrust bearing side thereof; meansproviding for the application of fluid un der primary pressure to saidpiston area; a spring acting on the abutment in opposition to theprimary pressure; means providing a secondary piston area on the pistonvalve; means for supplying fluid under secondary pressure to thesecondary piston area; said secondary piston area being so disposedthat, with movement of the v piston valve in consequence of primarypressure change, the force of the resulting secondary pressure iseffective to restore the piston valve to neutral or cut-off position;and means utilizing fluid under pressure for spinning the piston valveand including a turbine rotor carried directly by the latter.

3. In combination, means providing fluid under primary pressure; acylinder having an inlet port supplied with fluid under pressure, anexhaust connection, and a secondary pressure port; means providing asupply passage communicating with the secondary pressure port; a pistonvalve mov able from an intermediate cut-off position, in one direction,to establish communication of the secondary pressure port with the inletport, and in the other direction, to establish communication of thesecondary pressure port with the exhaust connection; an abutmentproviding a primary piston area; a thrust bearing between one end of thepiston valve and the abutment; bellows means cooperating with theabutment to define a fluid-tight compartment whose interior surface isprovided in part by the primary piston area; means for supplying fluidunder primary.

pressure to said chamber; a spring acting on the abutment in oppositionto the primary pressure; means providing a secondary piston area on thepiston valve and facing in such a direction that pressure appliedthereto causes the .piston valve to follow the motion of the abutment;means providing for the application of fluid under secondary pressure tosaid secondary piston-area; and means for imparting spinning motion tothe piston valve.

4. In combination, means providing fluid under primary pressure; acylinder having an inlet port supplied with fluid under pressure, anexhaust connection, and a secondary pressure port; means providing asupply passage communicating with the secondary pressure port; a pistonvalve movable from intermediate cut-off position, in one direction, toestablish communication of the secondary port with the inlet port, andin the other direction, to establish communication of the secondaryport' with the exhaust connection; an abutment; a thrust bearing betweenone end of the piston valve and the abutment; said abutment having apiston face at the thrust bearing side thereof; means for applying fluidunder primary pressure to the abutment piston area; a spring acting onthe abutment in opposition to the primary pressure; means providing asecondary piston area on the piston valve and facing in the samedirection as that of the primary piston area; means for supplying'fluidunder secondary pressure to the secondary piston area; and meansutilizing fluid under pressure for spinning the piston valve andincluding a turbine rotor carried directly by the latter.

' 5. In combination, means providing fluid under primary pressure; amovable abutment having a primary piston area subject to fluid underprimary pressure; spring means acting on the abutment in opposition tothe fluid under primary pressure; a cylinder having an inlet portsupplied with fluid under pressure, an exhaust con, nection, anda'secondary pressure port; means providing a supply passagecommunicating with the secondary pressure port; a piston valve movablewith the abutment to place the secondary pressure port in communicationeither with the inlet port or with the exhaust connection to securevariation of fluid under secondary pressure in the supply passage; meansproviding a secondary piston area on the piston valve; means providingfor the application of fluid under secondary pressure to the pistonarea; said secondary piston area facing in such a direction that thesecondary pressure imposed thereon acts in a direction opposite to saidspring means; a thrust bearing between said abutment and the adjacentend of the piston valve; and means for imparting spinning motion to thepiston valve.

6. The combination with a prime mover having an admission valve, ofmeans for developing fluid under primary pressure which is a function ofthe prime mover speed; pressure supply means; a cylinder having an inletport communicating with the pressure supply means, having an exhaustconnection, and having a secondary or transformed pressure supply port;a piston valve for placing the secondary pressure port in communicationwith the inlet port or with the exhaust connection to vary the secondarypressure; means for moving the piston valve including primary andsecondary piston areas subject to primary and secondary pressures,respectively, and biasing means whose force opposes the force of theprimary pressure applied to the primary piston area; a servo-motor foradjusting said admission valve and including a pilot valve forcontrolling the admission and exhaust of motive fluid thereto; apressure responsive device for moving the servomotor pilot valve; apassage for supplying fluid under secondary pressure from said secondarypressure supply port to the pressure-responsive device; and scale springmeans exerting force on the servo-motor pilot valve such that a range ofsecondary pressures from a lower pressure to a higher pressure isrequired to move the pilot valve sufliciently to secure full range ofmovement of the servo-motor in one direction and from the higherpressure to the lower pressure for such movement in the other direction.

7. The combination with a prime mover having an admission valve, ofmeans for developing fluid under primary pressure dependent on the primemover speed; a cylinder having an inlet port supplied with fluid underpressure, an exhaust connection, and a secondary pressure port; meansproviding a supply passage communicating with the secondary pressureport; apiston valve movable to establish communication of the secondarypressure port either with the inlet port or with the exhaust connectionto provide a variable secondary pressure; a movable abutment having aprimary piston area subject to primary pressure; a spring exerting itsforce on the abutment in opposition to that of the fluid under primarypressure; abutment means between one end of the piston valve and themovable abutment and including a thrust bearing; means providing asecondary piston area for the piston valve and so supply passage andresponsive to secondary pressure.

8. In combination, means providing fluid under primary pressure; acylinder having an inlet port supplied with fluid under pressure, anexhaust connection, and a secondary pressure port; means providing asupply passage communicating with the secondary pressure port; a pistonvalve for placing the secondary pressure port in communication eitherwith the inlet port or with the exhaust connection to secure variationin secondary or transformed fluid pressure; means for actuating thepiston valve including primary and secondary piston areas; means forapplying fluid under primary pressure to the primary piston area; meansincluding an orifice for supplying fluid from said supply passage tosaid secondary piston area; and an accumulator in communication with thelast-named means at the secondarypiston area side of the orifice.

9. In combination, means providing fluid under primary pressure; acylinder having an inlet port supplied with fluid under pressure, anexhaust connection, and a secondary pressure supply port; meansproviding a supply passage communicating with the secondary pressureport; a piston valve movable from an intermediate cut-off position, inone direction, to establish communication of the supply port with theinlet port, and, in the other direction, to establish communication ofthe secondary port with the exhaust connection; spring means for movingthe piston valve in one direction; means responsive to fluid underprimary pressure and acting in opposition to the spring means to providemovement of the piston valve in the other direction; means providing asecondary piston area on the piston valve; means for supplying fluidunder secondary pressure to the secondary piston area and including anorifice; and an accumulator communicating with the lastnamed means atthe secondary piston area side of the orifice; said secondary pistonarea being so disposed that, with movement of the piston valve inconsequence of primary pressure change, the force of the resultingsecondary pressure is effective to restore the piston valve to neutralor cutoff position.

10. In combination, means providing fluid under primary pressure, apressure transformer uti 'zing fluid under primary pressure to provide asecondary or transformed fluid pressure, said transformer includingprimary and secondary piston areas, means for subjecting the primarypiston area to primary pressure, means providing a delivery passage forfluid under secondary or transformed pressure, means providing a branchpassage including an orifice for supplying fluid under secondarypressure from the delivery passage for action on the secondary pistonarea, and an air chamber communicating with the branch passage at thesecondary piston area side of the orifice.

11. In a prime mover, admission valve means,

means providing a primary fluid pressure varying as a function of theprime mover speed, means utilizing the primary pressure to provide atransformed or secondary pressure having normal predetermined relationwith respect to the primary pressure, means responsive to transformed orsecondary pressure to control the admission valve means, and meansresponsive to'exceeding a predetermined rate of primary pressure changeand speed change to cause change of secondary pressure at a greater ratethan that corresponding to the rate of primary pressure change to efiectquick adjustment of the valve means for normal speed of the prime moverfor the load condition.

12. The combination with a turbine having admission valve means; ofmeans for biasing the admission valve means in a closing direction;pressure responsive means for controlling the admission valve means;means for developing fluid under primary pressure which is a function ofthe turbine speed; a cylinder having an inlet port, an exhaustconnection, and a secondary pressure' port; a passage for supplyingfluid under high pressure to the inlet port; a piston valve movable toestablish communication of the secondary pressure port either with theinlet port or with the exhaust connection to secure variation intransformed or secondary pressure; means for imparting spinning motionto the piston valve; means providing a primary piston area subject toprimary pressure; abutment mean's between the means providing theprimary piston area and one end of the piston valve and including athrust bearing; a spring exerting its force on said abutment means inopposition to the force exerted thereon by-the primary pressure; meansproviding a piston area on the piston valve; means providing for theapplication of fluid under pressure to said secondary piston area; anoverspeed governor operated by the turbine; and means responsive tooperation of the overspeed governor to interrupt said high pressurepassage and to release the pressure in the secondary passage, so thatsaid biasing means may close the admission valve means.

13. The combination with a turbine having admission valve means; ofmeans for biasing the admission valve means in a closing direction;pressure responsive means for controlling the admission valve means;means for developing fluid under primary pressure which is a function ofthe turbine speed; a cylinder having an inlet port, an exhaustconnection, and a secondary pressure port; a passage for supplying fluidunder high pressure to the inlet port; a piston valve movable toestablish communication of the secondary pressure port either with theinlet port or with the exhaust connection to secure variation intransformed or secondary pressure; means for imparting spinning motionto the piston valve; means providing a primary piston area subject toprimary pressure; abutment means between the means providing the primarypiston area and one end of the piston valve and including a thrustbearing; a spring exerting its force on said abutment means inopposition to the force exerted thereon by the primary pressure; meansproviding a secondary piston area on the piston valve; means providingfor the application of secondary pressure to said secondary piston area;a branch passage supplied with fluid through an orifice from said highpressure passage; a pressure release passage connected to said secondarypassage; a valve in the release passage; a valve in said high pressurepassage and disposed between the branch connection and said cylinder; apressure-responsive device connected to said branch passage andefiective normally to maintain the secondary release pasage valve closedand the high pressure passage valve open; an overspeed governor operatedby the turbine; and means responsive to operation of the overspeedgovernor to release pressure. in said branch passage to cause operationof the lastnamed pressure responsive device to secure closure of thehigh pressure passage valve and opening of the secondary release passagevalve so that said biasing means may close the admission valve means.

14. The combination with a prime mover having admission valve means anda throttle valve, of biasing means for closing the admission valvemeans; pressure responsive means for controlling the admission valvemeans; means responsive to pressure for holding the throttle valve openagainst the force of biasing means; means for developing fluid underprimary pressure which is a function of the prime mover speed; meansincluding a passage providing a source of fluid under high pressure; asecondary pressure supply passage connected to said admission valvecontrolling means; a cylinder having high pressure, secondary pressure,and exhaust connections; said high pressure and secondary pressureconnections being connected to the high pressure and secondary pressurepassages; a piston valve movable in opposite directions in said cylinderto place the secondary pressure connection in communication either withthe high pressure connection or with the exhaust connection; means forimparting spinning motion to the piston valve; means providing a primarypiston area subject to primary pressure; abutment means between theprimary piston area providing means and one end of the piston valve andincluding a thrust bearing; a spring exerting force on the primarypiston area in opposition to the force exerted thereon by the primarypressure; means providing a secondary piston area on the piston valve;means providing for the application of secondary pressure to saidsecondary piston area; a branch passage supplied with fluid through anorifice from said high pressure passage and connected to the pressureresponsive means of the throttle valve; a pressure release passageconnected to said secondary passage; a normally closed valve in therelease passage; a normally open valve in said high pressure passagebetween said branch connection and said cylinder; a pressure responsivedevice connected to said branch passage and effective normally tomaintain the release passage valve closed and to maintain the highpressure passage valve open; an overspeed governor operated by the primemover; and means responsive to operation of the overspeed governor at apredetermined overspeed of the prime mover to release the pressure insaid branch passage to bring about closure of the throttle valve,closing of said high pressure passage valve, and opening of saidsecondary release passage valve so that said biasing means may close theadmission valve means.

15. The combination with a prime mover having an admission valve movedby a servo-motor and having means for developing fluid under pressurewhich varies as a function of the prime mover speed, of means responsiveto said fluid pressure to provide transformed fluid pressure bearingpredetermined relation with respect thereto, a passage for supplyingfluid under transformed pressure to the servo-motor to control theoperation of the latter, means providing an orifice in said passage torestrict the flow rate therethrough, and accumulator means incommunication with said passage between the orifice and the passage forsupplying fluid under secondary pressure to said servo-motor, an exhaustconnection, a piston valve for placing the secondary pressure supplypassage in communication with said supply means or with the exhaustconnection, means for imparting spinning motion to the piston valve,means for actuating the piston valve including primary and secondarypiston areas subject to said primary and secondary pressures,respectively, a passage for supplying fluid from the secondary passageto the secondary piston area and provided with an adjustable orifice, anaccumulator in communication with said supply passage between theorifice and the secondary piston area, an adjustable orifice in thesecondary supply passage, and an accumulator communicating with thesecondary supply passage between the lastnamed adjustable orifice andthe servo-motor.

ANTHONY F. SCHWENDNER.

